linux/drivers/base/memory.c
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   1/*
   2 * Memory subsystem support
   3 *
   4 * Written by Matt Tolentino <matthew.e.tolentino@intel.com>
   5 *            Dave Hansen <haveblue@us.ibm.com>
   6 *
   7 * This file provides the necessary infrastructure to represent
   8 * a SPARSEMEM-memory-model system's physical memory in /sysfs.
   9 * All arch-independent code that assumes MEMORY_HOTPLUG requires
  10 * SPARSEMEM should be contained here, or in mm/memory_hotplug.c.
  11 */
  12
  13#include <linux/module.h>
  14#include <linux/init.h>
  15#include <linux/topology.h>
  16#include <linux/capability.h>
  17#include <linux/device.h>
  18#include <linux/memory.h>
  19#include <linux/kobject.h>
  20#include <linux/memory_hotplug.h>
  21#include <linux/mm.h>
  22#include <linux/mutex.h>
  23#include <linux/stat.h>
  24#include <linux/slab.h>
  25
  26#include <linux/atomic.h>
  27#include <asm/uaccess.h>
  28
  29static DEFINE_MUTEX(mem_sysfs_mutex);
  30
  31#define MEMORY_CLASS_NAME       "memory"
  32
  33static int sections_per_block;
  34
  35static inline int base_memory_block_id(int section_nr)
  36{
  37        return section_nr / sections_per_block;
  38}
  39
  40static struct bus_type memory_subsys = {
  41        .name = MEMORY_CLASS_NAME,
  42        .dev_name = MEMORY_CLASS_NAME,
  43};
  44
  45static BLOCKING_NOTIFIER_HEAD(memory_chain);
  46
  47int register_memory_notifier(struct notifier_block *nb)
  48{
  49        return blocking_notifier_chain_register(&memory_chain, nb);
  50}
  51EXPORT_SYMBOL(register_memory_notifier);
  52
  53void unregister_memory_notifier(struct notifier_block *nb)
  54{
  55        blocking_notifier_chain_unregister(&memory_chain, nb);
  56}
  57EXPORT_SYMBOL(unregister_memory_notifier);
  58
  59static ATOMIC_NOTIFIER_HEAD(memory_isolate_chain);
  60
  61int register_memory_isolate_notifier(struct notifier_block *nb)
  62{
  63        return atomic_notifier_chain_register(&memory_isolate_chain, nb);
  64}
  65EXPORT_SYMBOL(register_memory_isolate_notifier);
  66
  67void unregister_memory_isolate_notifier(struct notifier_block *nb)
  68{
  69        atomic_notifier_chain_unregister(&memory_isolate_chain, nb);
  70}
  71EXPORT_SYMBOL(unregister_memory_isolate_notifier);
  72
  73static void memory_block_release(struct device *dev)
  74{
  75        struct memory_block *mem = container_of(dev, struct memory_block, dev);
  76
  77        kfree(mem);
  78}
  79
  80/*
  81 * register_memory - Setup a sysfs device for a memory block
  82 */
  83static
  84int register_memory(struct memory_block *memory)
  85{
  86        int error;
  87
  88        memory->dev.bus = &memory_subsys;
  89        memory->dev.id = memory->start_section_nr / sections_per_block;
  90        memory->dev.release = memory_block_release;
  91
  92        error = device_register(&memory->dev);
  93        return error;
  94}
  95
  96unsigned long __weak memory_block_size_bytes(void)
  97{
  98        return MIN_MEMORY_BLOCK_SIZE;
  99}
 100
 101static unsigned long get_memory_block_size(void)
 102{
 103        unsigned long block_sz;
 104
 105        block_sz = memory_block_size_bytes();
 106
 107        /* Validate blk_sz is a power of 2 and not less than section size */
 108        if ((block_sz & (block_sz - 1)) || (block_sz < MIN_MEMORY_BLOCK_SIZE)) {
 109                WARN_ON(1);
 110                block_sz = MIN_MEMORY_BLOCK_SIZE;
 111        }
 112
 113        return block_sz;
 114}
 115
 116/*
 117 * use this as the physical section index that this memsection
 118 * uses.
 119 */
 120
 121static ssize_t show_mem_start_phys_index(struct device *dev,
 122                        struct device_attribute *attr, char *buf)
 123{
 124        struct memory_block *mem =
 125                container_of(dev, struct memory_block, dev);
 126        unsigned long phys_index;
 127
 128        phys_index = mem->start_section_nr / sections_per_block;
 129        return sprintf(buf, "%08lx\n", phys_index);
 130}
 131
 132static ssize_t show_mem_end_phys_index(struct device *dev,
 133                        struct device_attribute *attr, char *buf)
 134{
 135        struct memory_block *mem =
 136                container_of(dev, struct memory_block, dev);
 137        unsigned long phys_index;
 138
 139        phys_index = mem->end_section_nr / sections_per_block;
 140        return sprintf(buf, "%08lx\n", phys_index);
 141}
 142
 143/*
 144 * Show whether the section of memory is likely to be hot-removable
 145 */
 146static ssize_t show_mem_removable(struct device *dev,
 147                        struct device_attribute *attr, char *buf)
 148{
 149        unsigned long i, pfn;
 150        int ret = 1;
 151        struct memory_block *mem =
 152                container_of(dev, struct memory_block, dev);
 153
 154        for (i = 0; i < sections_per_block; i++) {
 155                pfn = section_nr_to_pfn(mem->start_section_nr + i);
 156                ret &= is_mem_section_removable(pfn, PAGES_PER_SECTION);
 157        }
 158
 159        return sprintf(buf, "%d\n", ret);
 160}
 161
 162/*
 163 * online, offline, going offline, etc.
 164 */
 165static ssize_t show_mem_state(struct device *dev,
 166                        struct device_attribute *attr, char *buf)
 167{
 168        struct memory_block *mem =
 169                container_of(dev, struct memory_block, dev);
 170        ssize_t len = 0;
 171
 172        /*
 173         * We can probably put these states in a nice little array
 174         * so that they're not open-coded
 175         */
 176        switch (mem->state) {
 177                case MEM_ONLINE:
 178                        len = sprintf(buf, "online\n");
 179                        break;
 180                case MEM_OFFLINE:
 181                        len = sprintf(buf, "offline\n");
 182                        break;
 183                case MEM_GOING_OFFLINE:
 184                        len = sprintf(buf, "going-offline\n");
 185                        break;
 186                default:
 187                        len = sprintf(buf, "ERROR-UNKNOWN-%ld\n",
 188                                        mem->state);
 189                        WARN_ON(1);
 190                        break;
 191        }
 192
 193        return len;
 194}
 195
 196int memory_notify(unsigned long val, void *v)
 197{
 198        return blocking_notifier_call_chain(&memory_chain, val, v);
 199}
 200
 201int memory_isolate_notify(unsigned long val, void *v)
 202{
 203        return atomic_notifier_call_chain(&memory_isolate_chain, val, v);
 204}
 205
 206/*
 207 * The probe routines leave the pages reserved, just as the bootmem code does.
 208 * Make sure they're still that way.
 209 */
 210static bool pages_correctly_reserved(unsigned long start_pfn)
 211{
 212        int i, j;
 213        struct page *page;
 214        unsigned long pfn = start_pfn;
 215
 216        /*
 217         * memmap between sections is not contiguous except with
 218         * SPARSEMEM_VMEMMAP. We lookup the page once per section
 219         * and assume memmap is contiguous within each section
 220         */
 221        for (i = 0; i < sections_per_block; i++, pfn += PAGES_PER_SECTION) {
 222                if (WARN_ON_ONCE(!pfn_valid(pfn)))
 223                        return false;
 224                page = pfn_to_page(pfn);
 225
 226                for (j = 0; j < PAGES_PER_SECTION; j++) {
 227                        if (PageReserved(page + j))
 228                                continue;
 229
 230                        printk(KERN_WARNING "section number %ld page number %d "
 231                                "not reserved, was it already online?\n",
 232                                pfn_to_section_nr(pfn), j);
 233
 234                        return false;
 235                }
 236        }
 237
 238        return true;
 239}
 240
 241/*
 242 * MEMORY_HOTPLUG depends on SPARSEMEM in mm/Kconfig, so it is
 243 * OK to have direct references to sparsemem variables in here.
 244 */
 245static int
 246memory_block_action(unsigned long phys_index, unsigned long action, int online_type)
 247{
 248        unsigned long start_pfn;
 249        unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
 250        struct page *first_page;
 251        int ret;
 252
 253        first_page = pfn_to_page(phys_index << PFN_SECTION_SHIFT);
 254        start_pfn = page_to_pfn(first_page);
 255
 256        switch (action) {
 257                case MEM_ONLINE:
 258                        if (!pages_correctly_reserved(start_pfn))
 259                                return -EBUSY;
 260
 261                        ret = online_pages(start_pfn, nr_pages, online_type);
 262                        break;
 263                case MEM_OFFLINE:
 264                        ret = offline_pages(start_pfn, nr_pages);
 265                        break;
 266                default:
 267                        WARN(1, KERN_WARNING "%s(%ld, %ld) unknown action: "
 268                             "%ld\n", __func__, phys_index, action, action);
 269                        ret = -EINVAL;
 270        }
 271
 272        return ret;
 273}
 274
 275static int __memory_block_change_state(struct memory_block *mem,
 276                unsigned long to_state, unsigned long from_state_req,
 277                int online_type)
 278{
 279        int ret = 0;
 280
 281        if (mem->state != from_state_req) {
 282                ret = -EINVAL;
 283                goto out;
 284        }
 285
 286        if (to_state == MEM_OFFLINE)
 287                mem->state = MEM_GOING_OFFLINE;
 288
 289        ret = memory_block_action(mem->start_section_nr, to_state, online_type);
 290
 291        if (ret) {
 292                mem->state = from_state_req;
 293                goto out;
 294        }
 295
 296        mem->state = to_state;
 297        switch (mem->state) {
 298        case MEM_OFFLINE:
 299                kobject_uevent(&mem->dev.kobj, KOBJ_OFFLINE);
 300                break;
 301        case MEM_ONLINE:
 302                kobject_uevent(&mem->dev.kobj, KOBJ_ONLINE);
 303                break;
 304        default:
 305                break;
 306        }
 307out:
 308        return ret;
 309}
 310
 311static int memory_block_change_state(struct memory_block *mem,
 312                unsigned long to_state, unsigned long from_state_req,
 313                int online_type)
 314{
 315        int ret;
 316
 317        mutex_lock(&mem->state_mutex);
 318        ret = __memory_block_change_state(mem, to_state, from_state_req,
 319                                          online_type);
 320        mutex_unlock(&mem->state_mutex);
 321
 322        return ret;
 323}
 324static ssize_t
 325store_mem_state(struct device *dev,
 326                struct device_attribute *attr, const char *buf, size_t count)
 327{
 328        struct memory_block *mem;
 329        int ret = -EINVAL;
 330
 331        mem = container_of(dev, struct memory_block, dev);
 332
 333        if (!strncmp(buf, "online_kernel", min_t(int, count, 13)))
 334                ret = memory_block_change_state(mem, MEM_ONLINE,
 335                                                MEM_OFFLINE, ONLINE_KERNEL);
 336        else if (!strncmp(buf, "online_movable", min_t(int, count, 14)))
 337                ret = memory_block_change_state(mem, MEM_ONLINE,
 338                                                MEM_OFFLINE, ONLINE_MOVABLE);
 339        else if (!strncmp(buf, "online", min_t(int, count, 6)))
 340                ret = memory_block_change_state(mem, MEM_ONLINE,
 341                                                MEM_OFFLINE, ONLINE_KEEP);
 342        else if(!strncmp(buf, "offline", min_t(int, count, 7)))
 343                ret = memory_block_change_state(mem, MEM_OFFLINE,
 344                                                MEM_ONLINE, -1);
 345
 346        if (ret)
 347                return ret;
 348        return count;
 349}
 350
 351/*
 352 * phys_device is a bad name for this.  What I really want
 353 * is a way to differentiate between memory ranges that
 354 * are part of physical devices that constitute
 355 * a complete removable unit or fru.
 356 * i.e. do these ranges belong to the same physical device,
 357 * s.t. if I offline all of these sections I can then
 358 * remove the physical device?
 359 */
 360static ssize_t show_phys_device(struct device *dev,
 361                                struct device_attribute *attr, char *buf)
 362{
 363        struct memory_block *mem =
 364                container_of(dev, struct memory_block, dev);
 365        return sprintf(buf, "%d\n", mem->phys_device);
 366}
 367
 368static DEVICE_ATTR(phys_index, 0444, show_mem_start_phys_index, NULL);
 369static DEVICE_ATTR(end_phys_index, 0444, show_mem_end_phys_index, NULL);
 370static DEVICE_ATTR(state, 0644, show_mem_state, store_mem_state);
 371static DEVICE_ATTR(phys_device, 0444, show_phys_device, NULL);
 372static DEVICE_ATTR(removable, 0444, show_mem_removable, NULL);
 373
 374#define mem_create_simple_file(mem, attr_name)  \
 375        device_create_file(&mem->dev, &dev_attr_##attr_name)
 376#define mem_remove_simple_file(mem, attr_name)  \
 377        device_remove_file(&mem->dev, &dev_attr_##attr_name)
 378
 379/*
 380 * Block size attribute stuff
 381 */
 382static ssize_t
 383print_block_size(struct device *dev, struct device_attribute *attr,
 384                 char *buf)
 385{
 386        return sprintf(buf, "%lx\n", get_memory_block_size());
 387}
 388
 389static DEVICE_ATTR(block_size_bytes, 0444, print_block_size, NULL);
 390
 391static int block_size_init(void)
 392{
 393        return device_create_file(memory_subsys.dev_root,
 394                                  &dev_attr_block_size_bytes);
 395}
 396
 397/*
 398 * Some architectures will have custom drivers to do this, and
 399 * will not need to do it from userspace.  The fake hot-add code
 400 * as well as ppc64 will do all of their discovery in userspace
 401 * and will require this interface.
 402 */
 403#ifdef CONFIG_ARCH_MEMORY_PROBE
 404static ssize_t
 405memory_probe_store(struct device *dev, struct device_attribute *attr,
 406                   const char *buf, size_t count)
 407{
 408        u64 phys_addr;
 409        int nid;
 410        int i, ret;
 411        unsigned long pages_per_block = PAGES_PER_SECTION * sections_per_block;
 412
 413        phys_addr = simple_strtoull(buf, NULL, 0);
 414
 415        if (phys_addr & ((pages_per_block << PAGE_SHIFT) - 1))
 416                return -EINVAL;
 417
 418        for (i = 0; i < sections_per_block; i++) {
 419                nid = memory_add_physaddr_to_nid(phys_addr);
 420                ret = add_memory(nid, phys_addr,
 421                                 PAGES_PER_SECTION << PAGE_SHIFT);
 422                if (ret)
 423                        goto out;
 424
 425                phys_addr += MIN_MEMORY_BLOCK_SIZE;
 426        }
 427
 428        ret = count;
 429out:
 430        return ret;
 431}
 432static DEVICE_ATTR(probe, S_IWUSR, NULL, memory_probe_store);
 433
 434static int memory_probe_init(void)
 435{
 436        return device_create_file(memory_subsys.dev_root, &dev_attr_probe);
 437}
 438#else
 439static inline int memory_probe_init(void)
 440{
 441        return 0;
 442}
 443#endif
 444
 445#ifdef CONFIG_MEMORY_FAILURE
 446/*
 447 * Support for offlining pages of memory
 448 */
 449
 450/* Soft offline a page */
 451static ssize_t
 452store_soft_offline_page(struct device *dev,
 453                        struct device_attribute *attr,
 454                        const char *buf, size_t count)
 455{
 456        int ret;
 457        u64 pfn;
 458        if (!capable(CAP_SYS_ADMIN))
 459                return -EPERM;
 460        if (strict_strtoull(buf, 0, &pfn) < 0)
 461                return -EINVAL;
 462        pfn >>= PAGE_SHIFT;
 463        if (!pfn_valid(pfn))
 464                return -ENXIO;
 465        ret = soft_offline_page(pfn_to_page(pfn), 0);
 466        return ret == 0 ? count : ret;
 467}
 468
 469/* Forcibly offline a page, including killing processes. */
 470static ssize_t
 471store_hard_offline_page(struct device *dev,
 472                        struct device_attribute *attr,
 473                        const char *buf, size_t count)
 474{
 475        int ret;
 476        u64 pfn;
 477        if (!capable(CAP_SYS_ADMIN))
 478                return -EPERM;
 479        if (strict_strtoull(buf, 0, &pfn) < 0)
 480                return -EINVAL;
 481        pfn >>= PAGE_SHIFT;
 482        ret = memory_failure(pfn, 0, 0);
 483        return ret ? ret : count;
 484}
 485
 486static DEVICE_ATTR(soft_offline_page, S_IWUSR, NULL, store_soft_offline_page);
 487static DEVICE_ATTR(hard_offline_page, S_IWUSR, NULL, store_hard_offline_page);
 488
 489static __init int memory_fail_init(void)
 490{
 491        int err;
 492
 493        err = device_create_file(memory_subsys.dev_root,
 494                                &dev_attr_soft_offline_page);
 495        if (!err)
 496                err = device_create_file(memory_subsys.dev_root,
 497                                &dev_attr_hard_offline_page);
 498        return err;
 499}
 500#else
 501static inline int memory_fail_init(void)
 502{
 503        return 0;
 504}
 505#endif
 506
 507/*
 508 * Note that phys_device is optional.  It is here to allow for
 509 * differentiation between which *physical* devices each
 510 * section belongs to...
 511 */
 512int __weak arch_get_memory_phys_device(unsigned long start_pfn)
 513{
 514        return 0;
 515}
 516
 517/*
 518 * A reference for the returned object is held and the reference for the
 519 * hinted object is released.
 520 */
 521struct memory_block *find_memory_block_hinted(struct mem_section *section,
 522                                              struct memory_block *hint)
 523{
 524        int block_id = base_memory_block_id(__section_nr(section));
 525        struct device *hintdev = hint ? &hint->dev : NULL;
 526        struct device *dev;
 527
 528        dev = subsys_find_device_by_id(&memory_subsys, block_id, hintdev);
 529        if (hint)
 530                put_device(&hint->dev);
 531        if (!dev)
 532                return NULL;
 533        return container_of(dev, struct memory_block, dev);
 534}
 535
 536/*
 537 * For now, we have a linear search to go find the appropriate
 538 * memory_block corresponding to a particular phys_index. If
 539 * this gets to be a real problem, we can always use a radix
 540 * tree or something here.
 541 *
 542 * This could be made generic for all device subsystems.
 543 */
 544struct memory_block *find_memory_block(struct mem_section *section)
 545{
 546        return find_memory_block_hinted(section, NULL);
 547}
 548
 549static int init_memory_block(struct memory_block **memory,
 550                             struct mem_section *section, unsigned long state)
 551{
 552        struct memory_block *mem;
 553        unsigned long start_pfn;
 554        int scn_nr;
 555        int ret = 0;
 556
 557        mem = kzalloc(sizeof(*mem), GFP_KERNEL);
 558        if (!mem)
 559                return -ENOMEM;
 560
 561        scn_nr = __section_nr(section);
 562        mem->start_section_nr =
 563                        base_memory_block_id(scn_nr) * sections_per_block;
 564        mem->end_section_nr = mem->start_section_nr + sections_per_block - 1;
 565        mem->state = state;
 566        mem->section_count++;
 567        mutex_init(&mem->state_mutex);
 568        start_pfn = section_nr_to_pfn(mem->start_section_nr);
 569        mem->phys_device = arch_get_memory_phys_device(start_pfn);
 570
 571        ret = register_memory(mem);
 572        if (!ret)
 573                ret = mem_create_simple_file(mem, phys_index);
 574        if (!ret)
 575                ret = mem_create_simple_file(mem, end_phys_index);
 576        if (!ret)
 577                ret = mem_create_simple_file(mem, state);
 578        if (!ret)
 579                ret = mem_create_simple_file(mem, phys_device);
 580        if (!ret)
 581                ret = mem_create_simple_file(mem, removable);
 582
 583        *memory = mem;
 584        return ret;
 585}
 586
 587static int add_memory_section(int nid, struct mem_section *section,
 588                        struct memory_block **mem_p,
 589                        unsigned long state, enum mem_add_context context)
 590{
 591        struct memory_block *mem = NULL;
 592        int scn_nr = __section_nr(section);
 593        int ret = 0;
 594
 595        mutex_lock(&mem_sysfs_mutex);
 596
 597        if (context == BOOT) {
 598                /* same memory block ? */
 599                if (mem_p && *mem_p)
 600                        if (scn_nr >= (*mem_p)->start_section_nr &&
 601                            scn_nr <= (*mem_p)->end_section_nr) {
 602                                mem = *mem_p;
 603                                kobject_get(&mem->dev.kobj);
 604                        }
 605        } else
 606                mem = find_memory_block(section);
 607
 608        if (mem) {
 609                mem->section_count++;
 610                kobject_put(&mem->dev.kobj);
 611        } else {
 612                ret = init_memory_block(&mem, section, state);
 613                /* store memory_block pointer for next loop */
 614                if (!ret && context == BOOT)
 615                        if (mem_p)
 616                                *mem_p = mem;
 617        }
 618
 619        if (!ret) {
 620                if (context == HOTPLUG &&
 621                    mem->section_count == sections_per_block)
 622                        ret = register_mem_sect_under_node(mem, nid);
 623        }
 624
 625        mutex_unlock(&mem_sysfs_mutex);
 626        return ret;
 627}
 628
 629/*
 630 * need an interface for the VM to add new memory regions,
 631 * but without onlining it.
 632 */
 633int register_new_memory(int nid, struct mem_section *section)
 634{
 635        return add_memory_section(nid, section, NULL, MEM_OFFLINE, HOTPLUG);
 636}
 637
 638#ifdef CONFIG_MEMORY_HOTREMOVE
 639static void
 640unregister_memory(struct memory_block *memory)
 641{
 642        BUG_ON(memory->dev.bus != &memory_subsys);
 643
 644        /* drop the ref. we got in remove_memory_block() */
 645        kobject_put(&memory->dev.kobj);
 646        device_unregister(&memory->dev);
 647}
 648
 649static int remove_memory_block(unsigned long node_id,
 650                               struct mem_section *section, int phys_device)
 651{
 652        struct memory_block *mem;
 653
 654        mutex_lock(&mem_sysfs_mutex);
 655        mem = find_memory_block(section);
 656        unregister_mem_sect_under_nodes(mem, __section_nr(section));
 657
 658        mem->section_count--;
 659        if (mem->section_count == 0) {
 660                mem_remove_simple_file(mem, phys_index);
 661                mem_remove_simple_file(mem, end_phys_index);
 662                mem_remove_simple_file(mem, state);
 663                mem_remove_simple_file(mem, phys_device);
 664                mem_remove_simple_file(mem, removable);
 665                unregister_memory(mem);
 666        } else
 667                kobject_put(&mem->dev.kobj);
 668
 669        mutex_unlock(&mem_sysfs_mutex);
 670        return 0;
 671}
 672
 673int unregister_memory_section(struct mem_section *section)
 674{
 675        if (!present_section(section))
 676                return -EINVAL;
 677
 678        return remove_memory_block(0, section, 0);
 679}
 680#endif /* CONFIG_MEMORY_HOTREMOVE */
 681
 682/*
 683 * offline one memory block. If the memory block has been offlined, do nothing.
 684 */
 685int offline_memory_block(struct memory_block *mem)
 686{
 687        int ret = 0;
 688
 689        mutex_lock(&mem->state_mutex);
 690        if (mem->state != MEM_OFFLINE)
 691                ret = __memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE, -1);
 692        mutex_unlock(&mem->state_mutex);
 693
 694        return ret;
 695}
 696
 697/* return true if the memory block is offlined, otherwise, return false */
 698bool is_memblock_offlined(struct memory_block *mem)
 699{
 700        return mem->state == MEM_OFFLINE;
 701}
 702
 703/*
 704 * Initialize the sysfs support for memory devices...
 705 */
 706int __init memory_dev_init(void)
 707{
 708        unsigned int i;
 709        int ret;
 710        int err;
 711        unsigned long block_sz;
 712        struct memory_block *mem = NULL;
 713
 714        ret = subsys_system_register(&memory_subsys, NULL);
 715        if (ret)
 716                goto out;
 717
 718        block_sz = get_memory_block_size();
 719        sections_per_block = block_sz / MIN_MEMORY_BLOCK_SIZE;
 720
 721        /*
 722         * Create entries for memory sections that were found
 723         * during boot and have been initialized
 724         */
 725        for (i = 0; i < NR_MEM_SECTIONS; i++) {
 726                if (!present_section_nr(i))
 727                        continue;
 728                /* don't need to reuse memory_block if only one per block */
 729                err = add_memory_section(0, __nr_to_section(i),
 730                                 (sections_per_block == 1) ? NULL : &mem,
 731                                         MEM_ONLINE,
 732                                         BOOT);
 733                if (!ret)
 734                        ret = err;
 735        }
 736
 737        err = memory_probe_init();
 738        if (!ret)
 739                ret = err;
 740        err = memory_fail_init();
 741        if (!ret)
 742                ret = err;
 743        err = block_size_init();
 744        if (!ret)
 745                ret = err;
 746out:
 747        if (ret)
 748                printk(KERN_ERR "%s() failed: %d\n", __func__, ret);
 749        return ret;
 750}
 751
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